Of course it is useful. PHP still plays an important role in web development, especially for CMS and e-commerce platforms. 1. The threshold for PHP is low, the syntax is intuitive, and suitable for beginners to get started; 2. It is widely used in dynamic web development, such as user login, form submission and other functions; 3. It can build an API interface, which is more efficient with the Laravel framework; 4. It supports CMS customization, such as WordPress plug-in and theme development; 5. It can write automated task scripts, such as data crawling and report generation; 6. Learning suggestions include mastering basic syntax, combining database exercise projects, using mainstream frameworks, focusing on security defense and referring to open source projects. PHP is highly practical and has a mature ecological environment, and is still widely used in small and medium-sized projects.

Annotations should be avoided in PHP development: 1. Do not comment sensitive information, such as database passwords or API keys, because these will still be exposed. It is recommended to use environment variables and add .gitignore; 2. Avoid outdated or incorrect comments. When modifying the code, you need to update the comments simultaneously to ensure the description is accurate; 3. Do not write meaningless comments. If you add redundant instructions to simple assignment statements, comments should be added in complex logic; 4. Do not replace PHPDoc document comments with ordinary comments. It is recommended to use standard formats to support IDE prompts and maintain structured information.

To run the PHP website on your local computer, you need to install PHP and Apache. Windows users download Apache and configure httpd.conf, then download PHP and modify the configuration file to load the PHP module; macOS/Linux users can use Homebrew or apt command to install. Finally, create an info.php file in the root directory of the website and test whether it is successful.

Comments cannot be careless because they want to explain the reasons for the existence of the code rather than the functions, such as compatibility with old interfaces or third-party restrictions, otherwise people who read the code can only rely on guessing. The areas that must be commented include complex conditional judgments, special error handling logic, and temporary bypass restrictions. A more practical way to write comments is to select single-line comments or block comments based on the scene. Use document block comments to explain parameters and return values at the beginning of functions, classes, and files, and keep comments updated. For complex logic, you can add a line to the previous one to summarize the overall intention. At the same time, do not use comments to seal code, but use version control tools.

PHP is suitable for beginners to quickly build local development environments. Use integrated tools such as XAMPP, WAMP or MAMP to install Apache, MySQL and PHP in one click. The project files can be accessed through localhost by putting them in the htdocs directory; 1. Download and install integrated environment tools; 2. Put the project files into the htdocs directory; 3. Browser access corresponding paths to test and run; you can also install PHP separately and configure environment variables, run php-Slocalhost:8000 through the command line to start the built-in server for quick debugging; create a new index.php and write an echo statement to output content, and add variables and condition judgment to experience logical processing capabilities. The key to getting started with PHP is to do it by hand.

When using if/else control structure for conditional judgment in PHP, the following points should be followed: 1. Use if/else when different code blocks need to be executed according to the conditions; 2. Execute if branches if the condition is true, enter else or elseif if they are false; 3. When multi-conditional judgment, elseif should be arranged in logical order, and the range should be placed in front of the front; 4. Avoid too deep nesting, it is recommended to consider switch or reconstruction above three layers; 5. Always use curly braces {} to improve readability; 6. Pay attention to Boolean conversion issues to prevent type misjudgment; 7. Use ternary operators to simplify the code in simple conditions; 8. Merge and repeat judgments to reduce redundancy; 9. Test boundary values to ensure the complete logic. Mastering these techniques can help improve code quality and stability.

The key to installing PHP is to clarify the usage scenario and system environment. 1. Determine the operating system and PHP version: Windows can use XAMPP or WAMP, macOS recommends Homebrew, Linux is installed through apt/yum, and it is recommended to choose version 8.1 or 8.2. 2. Local development environment construction: XAMPP, MAMP or Docker is recommended. You can also install it with Homebrew and verify it with php-v. 3. Server installation PHP: Taking Ubuntu as an example, execute aptupdate and installation commands and restart Apache/Nginx, and run through info.php test. 4. Frequently asked questions: Pay attention to extension activation, consistent path, permission settings and

The reasons and ways to avoid the occurrence of "undefinedindex" error: 1. The reasons include accessing GET/POST parameters that are not passed, array logic errors, variable index not set, etc.; 2. Solutions include using isset() to check whether the key exists, using array_key_exists() to judge, and using the empty merge operator to provide default values; 3. Development suggestions include unified parameter verification, enabling debugging prompts, viewing data structures, and using IDE inspection functions.